When is a 904 too small?

Well there are 5 disc direct drums made for the 904, so I don't know what "limit" they're talkin about. Bucky Hess used to run a 904 in his SS/A Cuda.......with a Hemi. I think it went 8s and then he went to something else. Course, it was a build mojo. I would think you could build a 904 easily to withstand 600 HP on a pretty affordable budget.